Hydromechanical elastomeric force amplifier

ABSTRACT

This hydromechanical elastomeric force amplifier has a casing containing two elongated preferably cylindrical force input and output chambers connected to one another by ports. Both chambers contain a hydraulic working fluid, such as a hydraulic oil. The force-input chamber has a reciprocable force-input or energizing plunger slidably mounted therein. The force-output chamber contains a reciprocable force-output or load-bearing plunger slidably mounted therein and this preferably is of the same diameter as the force-input plunger. Interposed between a socket in the inner end of the force-output plunger and a corresponding socket in a boss in the opposite cylinder head of the forceoutput chamber is an elongated approximately cylindrical forcetransforming actuator of an elastic deformable material compatible with the working fluid and vice versa, and preferably provided with slide guide bearings. This elastomeric actuator in its relaxed condition is spaced radially away from the side wall or cylinder bore of the force-output chamber, and is so connected to the force-output cylinder head and the force-output or loadbearing plunger that its opposite ends and the adjacent end portions of the plunger and cylinder head are not exposed to contact with the hydraulic working fluid, with the result that only the side surfaces thereof are so exposed and thereby subjected to the action of the hydraulic working fluid in the force-output chamber. In operation, let it be assumed that before operating the forceinput plunger, a sufficiently heavy load is imposed upon the force-output or load-bearing plunger to cause the resulting descent of the force-output plunger and in turn to deform the elastic deformable actuator axially, with a consequent lateral expansion or bulging thereof. Actuation of the force-input plunger now moves hydraulic working fluid under pressure from the force-input chamber through the side wall ports thereof into the force-output chamber, where it acts against only the bulging side walls of the elastic deformable actuator, causing inward yeilding thereof back toward its original relaxed shape, with a resulting reduction in its diameter and with a consequent axial elongation thereof by the rearrangement of the molecules of its elastic deformable material. This elongation produces a consequent outward sliding motion of the force-output or load-bearing plunger, with an amplification of the force applied to the forceinput plunger. Thus, in a test of the actual device, a 40-pound weight placed on top of the force-output or load-bearing plunger has been lifted thereby a certain distance by means of the operator&#39;&#39;s finger depressing the force input plunger of the same diameter the same distance. It is not necessary, however, for both plungers to be of the same diameters.

United States Patent [191 Kustusch [111 3,760,588 [451 Sept. 25, 1973 HYDROMECHANICAL ELASTOMERIC FORCE AMPLIFIER Paul W. Kustusch, 666 Parker Ave. Apt. 312, Detroit, Mich. 48214 22 Filed: Jan. 3, 1972 211 App]. No.: 214,843

[76] Inventor:

[52] US. Cl. 60/54.5 R, 254/93 R [51] Int. Cl. Fl5b 7/00 [58] Field of Search 60/545, 54.6 R,

60/1, 54.5 H, 54.6 H, 54.5 HA, 54.6 HA; 185/37, 4, 27; 92/89, 90; 251/57; 254/93 Primary Examiner-Martin P. Schwadron Assistant Examiner-A. M. Zupcic Attorney-Willis Bugbee [S 7] ABSTRACT This hydromechanical elastomeric force amplifier has a casing containing two elongated preferably cylindrical force input and output chambers connected to one another by ports. Both chambers contain a hydraulic working fluid, such as a hydraulic oil. The force-input chamber has a reciprocable force-input or energizing plunger slidably mounted therein. The force-output chamber contains a reciprocable force-output or loadbearing plunger slidably mounted therein and this preferably is of the same diameter as the force-input plunger. Interposed between a socket in the inner end of the force-output plunger and a corresponding socket in a boss in the opposite cylinder head of the forceoutput chamber is an elongated approximately cylindrical force-transforming actuator of an elastic deformable material compatible with the working fluid and vice versa, and preferably provided with slide guide bearings. This elastomeric actuator in its relaxed condition is spaced radially away from the side wall or cylinder bore of the force-output chamber, and is so connected to the force-output cylinder head and the forceoutput or load-bearing plunger that its opposite ends and the adjacent end portions of the plunger and cylinder head are not exposed to contact with the hydraulic working fluid, with the result that only the side surfaces thereof are so exposed and thereby subjected to the action of the hydraulic working fluid in the force-output chamber.

In operation, let it be assumed that before operating the force-input plunger, a sufficiently heavy load is imposed upon the force-output or load-bearing plunger to cause the resulting descent of the force-output plunger and in turn to deform the elastic deformable actuator axially, with a consequent lateral expansion or bulging thereof. Actuation of the force-input plunger now moves hydraulic working fluid under pressure from the force-input chamber through the side wall ports thereof into the force-output chamber, where it acts against only the bulging side walls of the elastic deformable actuator, causing inward yeilding thereof back toward its original relaxed shape, with a resulting reduction in its diameter and with a consequent axial elongation thereof by the rearrangement of the molecules of its elastic deformable material. This elongation produces a consequent outward sliding motion of the force-output or load-bearing plunger, with an amplification of the force applied to the force-input plunger. Thus, in a test of the actual device, a 40-pound weight placed on top of the force-output or load-bearing plunger has been lifted thereby a certain distance by means of the operators finger depressing the force input plunger of the same diameter the same distance. It is not necessary, however, for both plungers to be of the same diameters.

7 Claims, 10 Drawing Figures [451 Sept. 25, 1973 United States Patent [191 Kustusch I-IYDROMECHANICAL ELASTOMERIC FORCE AMPLIFIER SUMMARY OF THE INVENTION A hydromechanical elastomeric force-amplifier of the above-described construction has many useful applications for force amplification, especially where space is at a premium for housing such devices. Useful applications of this device are found, for example, in aircraft, submarines, transport vehicles and other mechanisms such as servo systems, where force amplification is required by instrumentalities of small sizes in comparison with the mechanical advantage which they can accomplish.

In the drawings:

FIG. 1 is a central longitudinal section through a hydromechanical elastomeric force amplifier, according to one form of the invention, with the moving parts in their relaxed condition in the absence of either a load or input force;

FIG. 2 is a cross-section on an enlarged scale, taken along the line 2-2 in FIG. 1;

FIG. 3 is an enlarged side elevation of a slide guide bearing used in the devices shown in FIGS. 1 and 2;

FIG. 4 is an end elevation of the slide guide bearing shown in FIG. 3;

FIG. 5 is a view similar to FIG. 1 but wherein a load, shown as a weight, has been applied to the force-output plunger prior to the application of an input force, showing the consequent lateral expansion or bulging of the elastic deformable actuator;

FIG. 6 is a view similar to FIGS. 1 and 5, but showing the relative positions of the working parts after a restorative input force has been applied to the force-input plunger and thence to the hydraulic working fluid in the input and output chambers, with a consequent radially-inward restorative deformation of the resilient elastomeric force-transforming actuator, with a consequent lifting of the load or weight and the accomplishment of a hydromechanical elastomeric force amplification;

FIG. 7 is a diagrammatic longitudinal section through the force-output cylinder similar to FIGS. 1, 5 and 6, showing, in its relaxed state, an elastomeric actuator of slightly less diameter than the diameter of the output plunger, the downward extension of whose cylindrical outer surface is herein termed the median cylinder;"

FIG. 8 is a view similar to FIG. 7 but showing the elastomeric actuator deformed laterally beyond the median cylinder by the application of a sufficiently heavy load;

FIG. 9 is a view similar to FIG. 7 but showing an elastomeric actuator of the same diameter as the force output plunger, hence of the same diameter as the median cylinder, in its relaxed state; and

FIG. 10 is a view similar to FIG. 9 but showing the action of various force components on the elastomeric actuator deformed laterally beyond the median cylinder by the application of a sufficiently heavy load.

CONSTRUCTION OF THE INVENTION Referring to the drawings in detail, FIG. 1 shows a hydromechanical elastomeric force amplifier, generally designated 10, constructed and arranged according to one form of the invention and consisting of a hollow casing 12 containing a casing chamber 15. The casing 12 is made up of a force input cylinder portion 14 and a force output cylinder portion 16. The casing chamber 15 is subdivided into force-input and force-output chambers 18 and 20 provided with bores or sidewall surfaces 19 and 21 contained within the input and output cylinder portions 14 and 16 respectively. The force-input and force-output chambers 18 and'20 are preferably although not necessarily of cylindrical shape and are interconnected by upper and lower side wall ports 22. The casing chamber 15 is filled with a suitable hydraulic working fluid 24. Reciprocably mounted in an elongated guide bore 26 in an input cylinder head 28, which with a suitable seal is bolted to the force input cylinder portion 14, is a force-input plunger 30 having a cylindrical side surface 31 and upper and lower end surfaces 32 and 34 respectively. Similarly mounted in an elongated guide bore 36 in an output cylinder head 38, which with a suitable seal is bolted to the output cylinder portion 16, is a force output plunger 40 having a cylindrical side surface 41 and upper and lower end surfaces 42 and 44 respectively, the latter being in the form of a socket 45 in an enlarged head 46 at the lower or inner end of the output plunger 40 surrounded by an annular face 47. The output chamber 20 at its lower end is closed by a lower cylinder head 48 which with a suitable seal is bolted thereto and contains an upwardly-projecting central cup-shaped boss or abutment 50 with a socket 52 therein surrounded by an annular face 53.

Snugly mounted in the sockets 44 and 52 are the reduced diameter upper and lower ends 54 and 56 of an elastic deformable or elastomeric actuator, generally designated 58. The body of the elastomeric actuator 58 is of approximately the same diameter as the head 46 and boss 50 so as to leave no end portion of the actuator 58, the plunger head 46 or the cylinder head boss 50 exposed to the action of the hydraulic working fluid, which fills all portions of the casing chamber 15. The body 60 is provided with circumferentially-spaced elongated grooves 62 (FIG. 2) ineach of which is slidably mounted an elongated slide guide bearing, generally designated 64 (FIGS. 3 and 4). The body 60 possesses an approximately cylindrical exposed outer side surface 65 and a central cylindrical cavity 67. The cavity 67 not only enhances the flexibility of the actuator body 60 to deformation, but also improves heat transfer from the body 60 through the air-filled cavity 67 to the metallic cylinder head 48 and plunger 40 for dissipation thereof.

Each slide guide bearing 64 consists of an elongated bar 66 of steel, suitably heat-treated after being provided with an elongated partially cylindrical channel 68 in the outer side 70 thereof. Each channel 68 is of slightly greater extent than a semi-cylinder'and is disposed parallel to the bottom surface 72 and to the opposite side surfaces 74 of the bar 66. Slidably mounted in the groove 68 of the bar 66, the outer side 70 of which optionally has inclined edge surfaces 76, is a cylindrical bearing element 78. The guide bearing body 66 in turn is slidably mounted in its respective groove 62, which is preferably and conveniently of rectangular cross-section. As a consequence, when the elastic deformable actuator 58 is'longitudinally deformed and consequently laterally expanded by the application of an external load thereto (FIG. 5), the cylindrical bearing members 78 of the slide guide bearings 64 engage the side wall surface 21 of the force output chamber 20 to give bearing support to the elastomeric actuator 58. These slide guide bearings 64 prevent the body 60 from assuming an undulatory form during deformation and prevent actual contact thereof with the side surface 21 of the output cylinder portion 16 during operation.

OPERATION OF THE INVENTION In the operation of the invention (FIGS. 1, 5 and 6), let it be assumed that the moving parts of the hydromechanical elastomeric force-amplifier 10 are in their relaxed non-load-bearing positions shown in FIG. 1 and that the casing chamber has been filled with a suitable hydraulic working fluid 24, which is compatible with the elastomer of the actuator 58. Let it then be as sumed that a load, conveniently represented by a weight designated L, is impressed upon the upper surface 42 of the force-output plunger or load-bearing plunger 40 (FIG. 5). The downward force exerted by the load L impressed by the weight upon the plunger 40 is transmitted downward to the upper end portion 54 of the elastomeric force-transforming actuator 58. Since the lower end portion 56 of the actuator 58 is incapable of moving, being held immovable in the socket 52 of the lower cylinder head 48 acting as an abutment, the resultant deformation of the elastomeric actuator 58 causes its longitudinal length to be shortened, and its lateral diameter to be increased. As a result, as the load L is increased upon the force-output plunger 40, the elastomeric actuator 50 bulges laterally until the slide guide bearings 64 engage the output cylinder side wall 21. As a consequence, the downward motion of the force-output or load-bearing plunger 40 displaces hydraulic fluid from the output chamber through the ports 22 into the force-input chamber 18, acting upon the lower end surface 34 of the force-input or energizing plunger 30, causing it to rise as shown in FIG. 5, in accordance with Pascals Law. A sufficient input force F is now applied to the force-input or energizing plunger 30 to move the latter downward to the position shown in FIG. 6, displacing hydraulic fluid 24 through the ports 22 from the force-input chamber 18 to the force-output chamber 20. There it acts against the exposed bulged side surface 65 of the body 60, but against the opposite ends 54 and 56 of the body 60 because these ends are inaccessible to the hydraulic fluid by being hidden within their respective sockets 44 and 52.

As a result, the bulged side surface 65 is deformed inward radially and the rearrangement of its molecules causes it to elongate axially until the body 60 reassumes its original substantially cylindrical configuration of FIG. 1, as shown in FIG. 6. Even though the force input piston 30 has traveled only the same distance downward (FIG. 6) as it had previously moved upward (FIG. 5), yet a mechanical advantage and force amplification has been obtained as discussed below. This action occurs by Le Chateliers Law, which states that the equilibrium of a system, when displaced by a stress, is displaced in such a way as to tend to relieve the stress.

Since the hydraulic fluid selected as the working fluid in the casing chamber 15 also has a lubricant action, the hydromechanical elastomeric force amplifier 10 never has to be lubricated. Moreover, the length of the elastomeric cylinder constituting the body 60 determines the length of stroke which is imparted to the force output plunger 40. Since the input and output plungers 30 and 40 are assumed to have equal diameters, the input plunger 30 will still be required to make the same length of stroke in order to restore the upper end surface 42 of the force output plunger 40 to its original position shown in FIG. 1 without the load and in FIG. 6 with the applied load.

The elastomeric material selected for the actuator 58 must possess this property of reassuming its original shape, in effect reconstructing itself while so doing, and the hydraulic working fluid selected should be such as will not detrimentally affect the elastomeric material of the force-transforming actuator 58 and vice versa during the intended working life thereof.

Pascals Law, referred to above, states that pressure exerted upon any part of an enclosed liquid is transmitted undiminished and equally in all directions therein.

THEORY UNDERLYING THE INVENTION The operation of the hydromechanical elastomeric force actuator 10 of the present invention depends on the fact that an elastomer, such as natural rubber, does not substantially compress up to an applied pressure of approximately 2,000 pounds per square inch but only deforms, and that it resumes its original shape and condition when the deforming force is removed. It is believed that every time an elastomer is thus deformed, a rearrangement of the molecules occurs therein and that where the elastomer is compounded with other materials, such as carbon black and manganese salts, crystals are formed which interlock during deformation and retard response of the elastomer to the action of the deforming force. In the present invention, the cylindrical surface 41 of the force-output or load-bearing plunger 40 is herein termed the median surface.

In actual practice, as shown in FIGS. 7 and 8, the relaxed cylindrical surface 65 of the elastomeric actuator 58 is preferred to be slightly smaller in diameter than the median surface 41 of the force output plunger 40. As a consequence, when a sufficiently heavy load is applied to the force-output or load-bearing plunger 40, the bulging of the middle portion of the surface 65 of the elastomeric actuator 58 extends outward beyond the side surface or median surface 41 of the forceoutput plunger 40 (FIG. 8), so that the projection upward, as in descriptive geometry, of the maximum outward bulge defines, with the cylindrical plunger outer surface or median surface 41 of the force-output or load-bearing plunger 40, an annular area. During operation this annular area is acted upon, under Pascals Law, by the hydraulic pressure in the chamber 20 to oppose the outward motion of the force output plunger 40 and thus detracts from the mechanical efficiency of the amplifier 10. If, however, the diameter of the cylindrical outer surface 65 of the elastomeric body 60 of the actuator 58 in its relaxed condition is less than the diameter of the force-output plunger cylindrical surface or median surface 41, the minimum bulge occurs therebeyond, and the minimum retardative effect occurs because the projected annulus is of minimum size (FIG. 8).

On the other hand, where the cylindrical side surface of the elastomeric body 60 of the elastomeric actuator 58 is of the same diameter as the cylindrical side surface or median surface 41 of the force-output or load-bearing plunger 40 (FIG. 9), when a sufficiently heavy load is applied to the force output plunger 40 (FIG. 10), the resulting bulge of the middle portion of the deformed body 60 extends much farther outward beyond the cylindrical side surface or median surface 41 of the plunger 40, with the result that the projection thereof upward relatively to the cylindrical surface 41 results in a much larger annulus with a considerably greater area and with a consequently greater retardative effect upon the output of the force-output or loadbearing plunger 40. It is therefore advisable, for the greatest efficiency, to maintain the relaxed diameter of the body 60 less than the diameter of the cylindrical surface or median surface 41 of the force output plunger 40. In other words, when the cross-sectional area of the bulgingly-deformed elastomeric body 60 exceeds the cross-sectional area of the force output plunger 40, a retardative area in the form of an annulus is created and the hydraulic pressure acting thereon at V and V (FIGS. 8 and 10). reduces the restorative effect of the forces acting laterally at V and V Experimentation has shown that a cylindrical configuration for the elastomeric actuator 60 is the most efficient configuration which after deformation resumes its original shape under hydraulic pressure. If an elastomeric ball, however, is similarly deformed in the chamber 20, it does not resume its original shape under hydraulic pressure because the opposing forces acting against the greater upper and lower areas of the laterally-bulged ball exceed the annular area around the ball. Experimentation has also shown that for the most advantageous response, the cross-sectional area of the elastomeric body 60 should be a cylinder whose crosssectional area when deformed does not exceed three times the cross-sectional area of the force output of the load bearing plunger.

When the area of the above-mentioned annulus equals the area of the deformed cylindrical portion of the deformed actuator 58, a pressure area equilibrium exists, without hydromechanical advantage (neglecting the effect of crystal lock within the elastomer). When, however, the cylindrical area of the deformed elastomeric actuator 58 exceeds the area of the annulus by a ratio of more than one-to-one, a hydromechanical advantage occurs, and is very pronounced when this ratio is equal to or greater than three-to-one or more (also neglecting such crystal lock effect). The application of lateral force to the bulged elastomeric actuator 58 also results in an additional retardative effect upon mechanical efficiency, due to internal friction arising within the elastomer as a result of the conversion of lateral or radial forces into longitudinal or axial forces. The combined detrimental or retardant effects upon the elastomer undergoing deformation as described above, can be termed elastomeric hysteresis.

An experimentally-derived empirical formula giving the energy output from the force-output plunger for a given energy input upon the force-input plunger, taking into account the elastomeric hysteresis is as follows:

E= (AXP/H) where E translated energy output from force-output or load-bearing plunger.

A side surface area of actuator in square units per one unit length.

X number of units of length in force-transforming actuator.

P input pressure per square inch.

H elastomeric hysteresis factor 6.66 (not a constant).

For example:

If A is 4 square inches in side surface area and X equals 4 inches in length and input pressure per square inch is I00 pounds, then E, the translated energy output, is 240 pounds.

Therefore, energy relationship or force-amplification ratio or mechanical advantage is 2.4 to l. The same relationship holds valid as the input pressure is increased. This relationship changes, however, whenever the X value changes, i.e. the more A units in the actuator, the greater is the mechanical advantage obtained. F urthermore, the more A units combined with greater pressure, the greater is the translated energy output. However, when A is 4 square inches and X is only one inch in length and the input pressure per square inch is pounds, then E, the translated output, is only 60 pounds (lifting capacity). This means, input would be greater than output, input being 100 pounds as against a 60 pounds output. Thus the output per unit is always less than the input except when such units are aligned in multiples. Then the number of units multiplied by the deficient result per A unit equals the final advantage. This is the reason for calling E the translated energy output.

I claim:

1. A hydromechanical elastomeric force amplifier comprising a casing structure having hydraulic fluid chamber means therein containing a hydraulic working fluid and having a force-input plunger bore and a forceoutput plunger bore communicating with said chamber means,

a force-input plunger reciprocably mounted in said force-input plunger bore and adapted to be operatively connected to a power source,

a force-output plunger reciprocably mounted in said force-output plunger bore and adapted to be operatively connected to a load to be moved,

a force-transforming actuator abutment disposed in said chamber means in axially-spaced relationship to said force-output plunger bore,

and an elastomeric force-transforming actuator disposed in said hydraulic fluid chamber means and having a body with axially-spaced opposite end portions disposed between and secured to the inner end of said force-output plunger and to said abutment respectively with said opposite end portions covered by said inner end of said force-output plunger and by said abutment respectively and substantially excluding said hydraulic working fluid from engagement with said opposite end portions of said actuator, said actuator having an elongated side surface extending between said end portions and exposed to contact with said hydraulic working fluid.

2. A hydromechanical elastomeric force amplifier, according to claim 1, wherein said abutment and said inner end of said force-output plunger are of substantially the same sizes at their junctions with said actuator and merge smoothly into said actuator without substantial shoulders therebetween and have sockets therein configured to fit said opposite end portions of said force-transforming actuator, and wherein said opposite end portions are snugly seated in said sockets.

3. A hydromechanical elastomeric force amplifier, according to claim 2, wherein said inner ends of said force-output plunger and said abutment have faces surguiding elements are mounted in said recesses.

6. A hydromechanical elastomeric force amplifier, according to claim 5, wherein said guiding elements comprise elongated bars with longitudinal channels therein and have elongated bearing members slidably mounted in said channels.

7. A hydromechanical elastomeric force amplifier, according to claim 1, wherein said actuator body is of substantially cylindrical configuration in its relaxed condition and is of bulged configuration intermediate its opposite ends in its loaded condition. 

1. A hydromechanical elastomeric force amplifier comprising a casing structure having hydraulic fluid chamber means therein containing a hydraulic working fluid and having a force-input plunger bore and a force-output plunger bore communicating with said chamber means, a force-input plunger reciprocably mounted in said force-input plunger bore and adapted to be operatively connected to a power source, a force-output plunger reciprocably mounted in said force-output plunger bore and adapted to be operatively connected to a load to be moved, a force-transforming actuator abutment disposed in said chamber means in axially-spaced relationship to said force-output plunger bore, and an elastomeric force-transforming actuator disposed in said hydraulic fluid chamber means and having a body with axiallyspaced opposite end portions disposed between and secured to the inner end of said force-output plunger and to said abutment respectively with said opposite end portions covered by said inner end of said force-output plunger and by said abutment respectively and substantially excluding said hydraulic working fluid from engagement with said opposite end portions of said actuator, said actuator having an elongated side surface extending between said end portions and exposed to contact with said hydraulic working fluid.
 2. A hydromechanical elastomeric force amplifier, according to claim 1, wherein said abutment and said inner end of said force-output plunger are of substantially the same sizes at their junctions with said actuator and merge smoothly into said actuator without substantial shoulders therebetween and have sockets therein configured to fit said opposite end portions of said force-transforming actuator, and wherein said opposite end portions are snugly seated in said sockets.
 3. A hydromechanical elastomeric force amplifier, according to claim 2, wherein said inner ends of said force-output plunger and said abutment have faces surrounding said sockets and wherein said opposite end portions of said force-transforming actuator engage said faces.
 4. A hydromechanical elastoMeric force amplifier, according to claim 1, wherein said actuator body has a cavity therein extending longitudinally thereof and closed off from entry of hydraulic working fluid therein.
 5. A hydromechanical elastomeric force amplifier, according to claim 1, wherein said actuator body has a plurality of circumferentially-spaced longitudinally-extending elongated recesses therein, and wherein guiding elements are mounted in said recesses.
 6. A hydromechanical elastomeric force amplifier, according to claim 5, wherein said guiding elements comprise elongated bars with longitudinal channels therein and have elongated bearing members slidably mounted in said channels.
 7. A hydromechanical elastomeric force amplifier, according to claim 1, wherein said actuator body is of substantially cylindrical configuration in its relaxed condition and is of bulged configuration intermediate its opposite ends in its loaded condition. 